The long-term goal of our research is to define the pathogenesis mechanisms of the most common causative agent of human airborne fungal infections, Aspergillus fumigatus. As the incidence of disease caused by A. fumigatus continues to rise and the mortality rate remains near 50%, new insights into the pathophysiology of these infections is needed. Elucidating the mechanisms by which A. fumigatus causes disease has great promise to identify new therapeutic strategies to improve patient outcomes. During the prior funding period we identified hypoxia, low oxygen levels, as a critical component of the infection site microenvironment in models of invasive pulmonary aspergillosis (IPA). Our data suggest that hypoxia contributes to host damage and poor IPA disease outcomes. These observations are consistent with data from many human diseases linking hypoxia with negative therapeutic results. Because we currently do not understand how hypoxia influences the outcome of fungal-host interactions, this is a need to know question given the significant association between hypoxia and poor human disease outcomes. The objective of this renewal proposal is to define molecular mechanisms of A. fumigatus hypoxia adaptation and test novel oxygen mediated therapeutic for improvement of IPA outcomes. Our central hypothesis is that inhibition of the hypoxia transcription factor SrbA mediated genetic network can be achieved to significantly improve IPA outcomes. The central hypothesis and objective of this research will be tested and accomplished by completing three specific aims. In aim 1, we will define the mechanism by which a new SrbA dependent transcription factor SrbB contributes to a novel hypoxia mediated iron uptake mechanism required for fungal virulence. In aim 2, we will define a previously unknown role for SrbA mediated fungal carbon catabolite repression in hypoxia adaptation and fungal virulence. In aim 3, we build on exciting preliminary data suggesting that manipulation of in vivo oxygen lung content through inhibition of the SrbA genetic network improves IPA outcomes. Successful completion of the experiments in this proposal will generate novel insights into mechanisms affecting fungal hypoxia adaptation, new insights into mechanisms of fungal virulence, and development of a new non-invasive therapeutic to improve IPA outcomes. These proposed studies are expected to be part of a continuum of research that will explore and define the tremendous therapeutic opportunities in understanding how fungi adapt to hypoxia.